In many loading dock areas, as well as in factories, warehouses, and other industrial areas in which moving equipment such as motorized forklifts are used, safety is important for the protection of personnel, equipment, and goods being handled. The danger of accidents increases in the vicinity of doorways or other passageways through which moving vehicles and/or personnel may travel at high rates of speed into other areas where they may collide with other vehicles, personnel, or obstacles.
There are inherent dangers associated with loading dock stations because loading docks typically are raised several feet with respect to the outside roadway and, moreover, trucks and semi-trailers are frequently moving immediately outside of the loading dock area. Because the passageways at loading dock stations involve high traffic situations to enable the loading or unloading of parked vehicles, it is desired to prevent forklifts from accidentally falling off the loading dock when a parked vehicle is not present. Forklifts are capable of traveling at high rates of speed while being difficult to handle and steer, particularly for inexperienced operators. Forklifts are also very heavy, which combined with their speed, results in large amounts of momentum and kinetic energy, making such forklifts difficult to stop.
Commercial and industrial doors are often subject to damage when they are inadvertently hit by forklifts or other large moving objects. Doors can sometimes prevent forklifts from traveling through the passageway, but many doors, particularly those made of fabric, plastic, or lightweight metal, may provide a false sense of security because they are not capable of stopping a forklift, and hence are subject to damage or disruption of the door as well as serious personal injury to the forklift driver and cargo, as well as other personnel, goods, and equipment which may be in the area.
Efforts have been made to provide substantially reinforced doors in an attempt to prevent such accidents, however, such doors are very expensive and the increased size and weight of the door are counterproductive because they result in slower travel of the door making it impossible to move the door either up or down fast enough to avoid accidents, as well as slowing the loading or unloading operation.
While there has been a long-felt need for a safety barrier to prevent accidental ingress or egress through a passageway, until recently such a barrier has been impractical. For example, a standard swinging gate mounted on a vertical post for pivotal movement about the vertical axis defined by the post, e.g., a barnyard gate, has not been practical in many industrial uses because of the time and effort involved in opening and closing such gates and because such gates can obstruct traffic even when in an open position.
Recently, a new safety gate assembly was invented and disclosed in U.S. patent application Ser. No. 07/799,032 (co-pending with this application) and also assigned to Rite-Hite Corporation. The safety gate of the latter application is hingedly mounted to a support member and pivotally movable in a substantially vertical plane. The pivotal safety gate, however, is inherently limited by the ratio of the width of the passageway to the height of the ceiling or other restrictions of the height to which the pivoting safety gate can travel.